Heuristic evaluation

Summary

Heuristic evaluation is a form of usability inspection where
usability specialists judge whether each element of a user
interface follows a list of established usability heuristics.
Expert evaluation is similar, but does not use specific
heuristics.

Usually two to three analysts evaluate the system with reference
to established guidelines or principles, noting down their
observations and often ranking them in order of severity.
The analysts are usually experts in human factors or HCI,
but others, less experienced have also been shown to report
valid problems.

A heuristic or expert evaluation can be conducted at various
stages of the development lifecycle, although it is preferable
to have already performed some form of context
analysis to help the experts focus on the circumstances
of actual or intended product usage.

Benefits

The method provides quick and relatively cheap feedback
to designers. The results generate good ideas for improving
the user interface. The development team will also receive
a good estimate of how much the user interface can be improved.

There is a general acceptance that the design feedback
provided by the method is valid and useful. It can also
be obtained early on in the design process, whilst checking
conformity to established guidelines helps to promote compatibility
with similar systems.

It is beneficial to carry out a heuristic evaluation on
early prototypes before actual users are brought in to help
with further testing.

Usability problems found are normally restricted to aspects
of the interface that are reasonably easy to demonstrate:
use of colours, lay-out and information structuring, consistency
of the terminology, consistency of the interaction mechanisms.
It is generally agreed that problems found by inspection
methods and by performance measures overlap to some degree,
although both approaches will find problems not found by
the other.

The method can seem overly critical as designers may only
get feedback on the problematic aspects of the interface
as the method is normally not used for the identification
of the ‘good’ aspects.

Method

This method is to identify usability problems based on established
human factors principles. The method will provide recommendations
for design improvements. However, as the method relies on
experts, the output will naturally emphasise interface functionality
and design rather than the properties of the interaction between
an actual user and the product.

Planning

The panel of experts must be established in good time for
the evaluation. The material and the equipment for the demonstration
should also be in place. All analysts need to have sufficient
time to become familiar with the product in question along
with intended task scenarios. They should operate by an agreed
set of evaluative criteria.

Running

The experts should be aware of any relevant contextual information
relating to the intended user group, tasks and usage of the
product. A heuristics briefing can be held to ensure agreement
on a relevant set of criteria for the evaluation although
this might be omitted if the experts are familiar with the
method and operate by a known set of criteria.

The experts then work with the system preferably using mock
tasks and record their observations as a list of problems.
If two or more experts are assessing the system, they should
not communicate with one another until the assessment is complete.
After the assessment period, the analysts can collate the
problem lists and the individual items can be rated for severity
and/or safety criticality.

Reporting

A list of identified problems, which may be prioritised with
regard to severity and/or safety criticality is produced.

In terms of summative output the number of found problems,
the estimated proportion of found problems compared to the
theoretical total, and the estimated number of new problems
expected to be found by including a specified number of new
experts in the evaluation can also be provided.

A report detailing the identified problems is written and
fed back to the development team. The report should clearly
define the ranking scheme used if the problem lists have been
prioritised.

More Information

Variations

Three to five experts are recommended for a thorough evaluation.
A quick review by one expert (often without reference to specific
heuristics) is usual before a user-based evaluation to identify
potential problems.

If usability experts are not available, other project members
can be trained to use the method, which is useful in sensitising
project members to usability issues.